Project Emerging: Zoophycos

“ … And yet we cannot hope to describe all of the natural happenings of our world; and thus impossible it seems to be to explain all of these unexplainable things …”

JL Alléon-Dulac, 1765, French naturalist (Opening Image). An ‘ammon horn’ sketch by Alleon-Dulac from 1765. Most probably an ammonite, Lytoceras sp, deriving from the Lyonnais quarries of France.

Our understanding of the Natural World will never be truly complete, yet seemingly, each day, we add another tiny fragment of knowledge, as some fresh academic paper adds to the long list of scientific bibliography. With just a few tiny pages, our understanding of the complexities of nature is focused ever clearer – Project Emerging is today’s paradigm, but by tomorrow, will be a fraction outdated. Yet, hard facts never alter; it is simply our conception of them which does.

If nature’s ‘big picture’ is observed through the prism of the great age of life on Earth, major patterns come to the fore. Simply speed up the sequences to see those differing, lively shapes adapt toward survival. Evolution, by whatever means, is the star factor, as remarkably, a harmony is found between both inert geologies and thriving ecosystems. Together, they all share ‘biosphere’.

Zoophycos from Bathonian limestones, Chasteuil, southern France.

At first, human intelligence desired to see a Creator. However, as the ever-questioning mind experimented and played, irrefutable results led on to discovery, and one academic discovery inspired the next as slowly, day by day, minute natural processes and cycles were untangled. The challenge of the project becomes a quest. With increasing speed, new answers are found and the emerging project diversifies towards individual topics. Then, fresh fossils are discovered; symbiotic lichens are analyzed; ‘new’ beetles are named; the multiverse is theorised; and viruses are deciphered. Therefore, various labours are divided, as our insight evolves further through both short academic, gradualist advances and through rapid, punctuated discovery. Science is rife.

To illustrate our historical and progressive understanding of life’s adaptation for survival, we could repeat the work of Stephen Jay Gould’s lineage of the horses (even Darwin had fossils of the Hipparion sp to examine, yet had failed to see them as a missing link); or the evolution of the dinosaurs; or evoke modern experimental processes and results upon the hapless fruit fly, not through profoundly deep time, but exceedingly short time. But no. We will play another card by describing our progressive, evolutionary understanding of the strange fossil phenomena named Zoophycos, as an historical fragment of palaeontology.

What is Zoophycos?

Today, there is a general agreement in considering it to be a trace fossil, or ichnofossil. It can be found within rocks ranging from the Cambrian to the Holocene, in various sediments and differing palaeoenvironments (Fig. 2). Zoophycos traces were seemingly produced by a deposit feeding organism, but this taxonomic attribution is still somewhat debated.

The initial hypothesis – of it being a trace fossil – was originally put forward in 1893, and it was named Spirophyton (not Zoophycos). Indeed, the very first attempts to untangle the mystery of the Zoophycos caused great confusion, as the large morphological complexity and variability of them, and other similar looking fossils, resulted in a mixed and unclear (ichno)taxonomy. Several synonyms appeared at the start of the 19th century – among them wonderful names like Fucoides circinatus, Zonarites, Gorgonia, Chondrites scoparius, Taonurus, Cancellophycus and Spirophyton. At this time, they were all considered to be seaweed fossils and, on some occasions, even a plant fossil. It was T Fuch who first provided some light on this problem in 1893, by suggesting the possibility that it was, in effect, a trace fossil. However, common agreement only truly emerged during the 1950s.

The importance of these intriguing trace fossils within palaeoenvironmental studies has now been widely recognised, yet a mixed bag of lingering ichnotaxonomic problems still hindered a clearer picture of Zoophycos and all the ‘related’ synonyms. As fossils of them accumulate, our comprehension of them relentlessly progresses, but just how complete is our understanding at this moment?

To this end, one of us (Davide Olivero) has recently tried to put order into the complex bustle of the Zoophycos ichnotaxonomic confusion – to unravel it all, sort it out and then look at Zoophycos anew. To achieve this sorting, we must attempt first to find the ‘holotype’, or type specimen of Zoophycos and, to do this, we must return to the original (mis)understanding of this enigmatic fossil. It is a fascinating challenge – a puzzle to solve.

A) Zoophycos villae. Original drawings from Massalongo 1855. The drawing was printed as a mirror reflection of the original fossil. B) Zoophycos villae Massalongo 1855. Natural History Museum of Verona, specimen number ICN2. C) Zoophycos villae Massalongo 1855. Natural History Museum of Verona, specimen number ICN1.

The name, Zoophycos, was proposed in 1855 by Abramo Massalongo, an Italian botanist who collected plant fossils in the Bolca area (mostly to the north of the town of Verona, in northern Italy). In his Latin monograph, Massalongo described in detail various specimens of what he considered to be plant fossils (later proven to be wrong). Beautiful drawings accompany his text allowing a clear view of the fossils that he had studied. However, a graphic representation is simply not enough, for it is the real artefacts that have to be examined. However, just where were they? Certain specimens from his collection were finally found in the Verona Natural History Museum, Italy. One of his fossils (Zoophycos caput medusae) was located in a desk mixed among various fossil plants (Fig. 3). This particular single ‘Zoophycos’ specimen was indeed correctly recognised by him, as a seaweed fossil!

And here lies a dilemma – according to laws of the International Code of Zoological and Botanical Nomenclatures, if the ‘type specimen’ is described as a fossil alga, the same name cannot be used for describing a trace fossil! In other words, the name, ‘Zoophycos’ cannot be used for describing ‘what-ever-they-are’ trace fossils. However, fortunately, Massalongo also simultaneously studied and depicted other fossil specimens (Fig. 4), proposing several sub-species alongside Zoophycos caput medusa (such as Z. Brianteus and Z. Villae). And the identification of these other species were effectively later shown to be trace fossils (not plants), and the initial naming of them as Zoophycos finally swings the balance to that name. So ‘Zoophycos’ is a trace fossil!

The names, Chondrites scoparius and Cancellophycus (both described between 1858 and 1873 from studies of the surroundings of Lyon, in France), and other specimens, such as Spirophyton (which were collected in the US), were originally considered as synonyms of Zoophycos. However, they too have now been extracted from the Zoophycos frame, for these differ somewhat from the typical Zoophycos holotype and must, therefore, be classed as different ichnofossils.

A better picture of Zoophycos

From this sifting of earlier research and untangling certain misinterpretations, we can now begin to get a picture of the true Zoophycos fossil and can, from this clear basis, begin to comprehend this astonishing and unusual trace fossil.

Zoophycos is a profound and complex burrow system (Fig. 5), with one single opening from the sea-floor. It appears as a thin layer of bioturbated (disturbed) sediment, constituting lamina, with an outline that can be either simple or lobate. The thickness of the layer is between 2mm and 10mm, and its width may reach up to 2m. The lamina is spirally coiled around a virtual central axis. The coil may be dextral or senestral, constructed either downward or upward within the sediment. Between one to five superimposed whorls can be seen.

Schematic drawing of a typical Zoophycos from the Middle Jurassic of southeastern France (from Olivero, 2003).

The structure is furrowed by a complex network of arched structures called ‘lamellae’. They represent the subsequent position of one single tunnel moving laterally through the sediment. This tunnel, at the margin of the lamina, constitutes the ‘marginal tube’.

Because of the various differences in the morphology and palaeoenvironmental setting of these ancient traces, we can suggest a diverse ichnospecies, all grouped within the ichnogenus Zoophycos (or Zoophycos group). Each ichnospecies is typical of a particular palaeoenvironment and may be the result of the slightly different behaviours of the trace maker species or even sub-species.

The next step of the emerging understanding of this specific context will be to clarify the significance of the individual zoophycos ichnospecies. And from this, will spin fresh challenges, not only the reconstructing of extinct palaeoenvironments, but also an attempt to understand the creatures that left these astonishing lifelines from such a distant time in the past – just what were they? This is a question surely for future scrutiny, as science, to answer Alleon-Dulac, indeed progressively describes the natural happenings of our world.

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